The Minnesota man who created a version of the Blaster Internet worm pleaded guilty last August in federal court, but this week lawyers on both sides of the case are arguing about the sentence he should receive.

Jeffrey Lee Parson is scheduled to be sentenced Friday by U.S. District Judge Marsha Pechman.

As part of his plea agreement, Parson admitted he downloaded the original Blaster worm in 2003 to his home computer in Hopkins, Minn., and bundled it with a “back-door” program that gave him access to computers. In court filings, prosecutors said that the worm infected about 48,000 computers and caused $1.2 million in damage.

The Blaster worm was designed to exploit a weakness in Microsoft’s Windows XP and Windows 2000 operating-system software. It was programmed to infect computers and then command the computers to attack a Web site owned by Microsoft at preset times. The worm did not bring down Microsoft’s Web site, however, because the company knew about the attack early on and took steps to prepare for it.

At the time of the plea agreement, Parson was facing 18 to 37 months in prison at a federal facility. But according to a presentencing note filed this week by the U.S. Attorney’s Office, Parson’s lawyers are planning to ask Pechman to change that sentence to six months in prison, six months at a community treatment center and six months of detention, followed by three years of supervision.

That didn’t sit well with the U.S. Attorney’s Office, which recommended in its filing that Parson be sentenced to 37 months. The office added that it would withdraw from the plea agreement if the judge sentenced Parson as his lawyers recommended. The case would then likely head to a trial.

“It’s a statement about how seriously law enforcement takes these kinds of crimes,” Assistant U.S. Attorney Annette Hayes said in an interview yesterday.

Parson’s attorneys did not return requests for comment yesterday.

Law enforcement seized computers Parson had used and were able to recover records of his online conversations with other hackers, according to the U.S. Attorney’s filing. In those conversations, Parson said he was looking for a copy of the Blaster worm and that he is thinking about spreading a version of it.

“Hehehe,” he wrote, “and watch me get caught.”

Parson unleashed the worm and left on a vacation with his family, according to the filing. When he returned, his friends told him that law enforcement was investigating the worm.

“In that case I’m gonna disappear for a while,” Parson responded in an online conversation. He also said he was going to erase everything on his computer’s hard drive. Later that same day, police arrived at Parson’s house with a search warrant.

In its presentencing filing, the U.S. Attorney’s Office recommended that Parson pay $622,500 in restitution to Microsoft and several hundred dollars to each of the 12 individual victims involved in the case. Microsoft had to spend money responding to the attacks against its Web site, as well as helping customers whose computers had been infected by the worm, the filing said.